The present invention relates to spectrum analyzers for determining the Fourier transform or spectral distribution of an electrical signal waveform. More specifically, it relates to a system for removing from the output of the spectrum analyzer spurious spectral components caused by nonlinearities in the spectrum analyzer.
Since nonlinear distortion of a signal waveform produces spectral components not present in the original undistorted signal, any nonlinearities in a spectrum analyzer will cause its output to include spurious spectral components.
This problem is especially prevalent in digital spectrum analyzers in which the signal to be analyzed is sampled and quantized using an analog-to-digital (A/D) converter and then applied to a digital fast Fourier transform (FFT) processor. Nonlinear distortion is introduced by jitter in the sampling time, quantization errors and nonlinearities in the A/D converter, and arithmetic truncation in the FFT processor. These nonlinearities cause the output of the FFT processor to show spurious spectral components not actually present in the signal being analyzed.